Aggregation behavior of chemically attached poly(ethylene glycol) to single-walled carbon nanotubes (SWNTs) ropes

The aggregation behavior of poly(ethylene glycol) (PEG)-grafted single-walled carbon nanotubes (SWNTs) was investigated by Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and high-resolution transmission electron microscopy (HR-TEM). The hybrid functional material was synthesized by producing carboxylic acid groups at nanotube ends and side-wall defect sites, which provide reaction sites for various guest species, followed by a reaction with hydroxyl-terminated PEG in various solvents. FTIR and TGA analyses confirm that the PEG chains were covalently attached to the functionalized SWNTs ropes. Transmission electron microscopy (TEM) images of the PEG-grafted SWNTs revealed two different morphologies, depending on solvent quality: PEG and SLANT segments self-organize into ring-like structure in which the aggregated PEG core is surrounded by SWNT bundles, when freshly prepared PEG-grafted SWNTs are cast from benzene/tetrahydrofuran solvent mixture. Instead, the hybrid polymers form a highly dispersed morphology in selective solvents for SwNTs. The novel aggregation mode originates from strong association of polymer chains with nanotubes, as in the aggregation behavior of microphase separated copolymers in dilute solution. (C) 2003 Elsevier B.V. All rights reserved.